The present invention relates to a fusing apparatus, such as used in electrostatographic printing.
In electrostatographic printing, commonly known as xerographic or printing or copying, an important process step is known as xe2x80x9cfusing.xe2x80x9d In the fusing step of the xerographic process, dry marking material, such as toner, which has been placed in imagewise fashion on an imaging substrate, such as a sheet of paper, is subjected to heat and/or pressure in order to melt or otherwise fuse the toner permanently on the substrate. In this way, durable, non-smudging images are rendered on the substrates.
Currently, the most common design of a fusing apparatus as used in commercial printers includes two rolls, typically called a fuser roll and a pressure roll, forming a nip therebetween for the passage of the substrate therethrough. Typically, the fuser roll further includes, disposed on the interior thereof, one or more heating elements, which radiate heat in response to a current being passed therethrough. The heat from the heating elements passes through the surface of the fuser roll, which in turn contacts the side of the substrate having the image to be fused, so that a combination of heat and pressure successfully fuses the image.
One practical problem with certain compact designs of xerographic or other printers relates to the unintended transfer of mechanical energy, such as vibration or a torque transient, originating at the fusing apparatus and traveling through a print sheet while another portion of the print sheet is still receiving marking material (e.g., toner or ink) at a marking station. This vibration or other mechanical energy can cause a print defect such as smearing at the marking station.
U.S. Pat. No. 5,822,668 describes a general configuration of a fuser module as used in a xerographic printer.
According to one aspect of the present invention, there is provided a method of conveying a sheet from a marking station to a nip formed by a first roll and a second roll. A leading edge of the sheet is directed toward the nip at an angle which causes the sheet to form an arc between the marking station and the nip as the leading edge of the sheet enters the nip. As a trailing edge of the sheet substantially exits the marking station, the sheet is straightened between the marking station and the nip.
According to another aspect of the present invention, there is provided a printing apparatus, comprising a marking station; a nip, formed by a first roll and a second roll; means for directing a leading edge of the sheet toward the nip at an angle which causes the sheet to form an arc between the marking station and the nip as the leading edge of the sheet enters the nip; and means for straightening the sheet between the marking station and the nip as a trailing edge of the sheet substantially exits the marking station.
According to another aspect of the present invention, there is provided a fusing apparatus for printing, comprising a first roll and a second roll, forming a nip therebetween; and a guide member, the guide member being positionable to direct a leading edge of a sheet toward the nip at an angle which causes the sheet to form an arc as the leading edge of the sheet enters the nip.
One practical problem with certain compact designs of xerographic or other printers relates to the unintended transfer of mechanical energy, such as vibration or a torque transient, originating at the fusing apparatus and traveling through a print sheet while another portion of the print sheet is still receiving marking material (e.g., toner or ink) at a marking station. This vibration or other mechanical energy can cause a print defect such as smearing at the marking station.